New inode PA is only added to i_prealloc_list in struct ext4_inode_info.
By implementation of EXT4_IOC_CONTROL_PA, we can create new inode PA freely.
So, the contiguous inode PA (both physical block and file offset are
bigger/smaller than the other inode PA's one) will be created more frequently.
Thus, ext4_mb_new_inode_pa() sorts and merges inode PA to get rid of
the contiguous one. This change will lead to saving memory usage, and
to improve the operation for i_prealloc_list.
The ffsb result on 20G SATA is as follows:
sequential (Transaction/sec)
read write create append delete
2.6.37-rc2+patch queue 2810.8 2727.9 2742.4 2752.4 10.8
apply this patch 2924.0 2800.0 2876.5 2889.4 11.3
There is some improvement, but I think it's the margin of error. So this patch
has an insignificant impact on the read/write performance.
Signed-off-by: Kazuya Mio <k-mio@xxxxxxxxxxxxx>
Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
---
fs/ext4/mballoc.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 103 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index e8effb6..cf501b3 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3416,6 +3416,49 @@ static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
}
+/**
+ * ext4_mb_merge_preallocations - Merge two preallocations
+ *
+ * @pa1: a preallocation
+ * @pa2: a preallocation that is absorbed by @pa1
+ *
+ * Merge PAs into @pa1 if possible.
+ * If success to merge, return 1. Otherwise return 0.
+ */
+static noinline_for_stack int
+ext4_mb_merge_preallocations(struct ext4_prealloc_space *pa1,
+ struct ext4_prealloc_space *pa2)
+{
+ struct super_block *sb = pa1->pa_inode->i_sb;
+ ext4_group_t pa1_grp, pa2_grp;
+
+ ext4_get_group_no_and_offset(sb, pa1->pa_pstart, &pa1_grp, NULL);
+ ext4_get_group_no_and_offset(sb, pa2->pa_pstart, &pa2_grp, NULL);
+
+ if (pa1_grp != pa2_grp)
+ return 0;
+ /* TODO: eliminate this restriction by moving all extents in @pa1 */
+ if ((pa1->pa_pstart > pa2->pa_pstart &&
+ pa1->pa_lstart < pa2->pa_lstart) ||
+ (pa1->pa_pstart < pa2->pa_pstart &&
+ pa1->pa_lstart > pa2->pa_lstart))
+ return 0;
+ if (pa1->pa_lstart + pa1->pa_len != pa2->pa_lstart &&
+ pa2->pa_lstart + pa2->pa_len != pa1->pa_lstart)
+ return 0;
+ if (pa1->pa_pstart + pa1->pa_len != pa2->pa_pstart &&
+ pa2->pa_pstart + pa2->pa_len != pa1->pa_pstart)
+ return 0;
+
+ pa1->pa_pstart = min(pa1->pa_pstart, pa2->pa_pstart);
+ pa1->pa_lstart = min(pa1->pa_lstart, pa2->pa_lstart);
+
+ pa1->pa_len += pa2->pa_len;
+ pa1->pa_free += pa2->pa_free;
+
+ return 1;
+}
+
/*
* creates new preallocated space for given inode
*/
@@ -3423,9 +3466,10 @@ static noinline_for_stack int
ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
{
struct super_block *sb = ac->ac_sb;
- struct ext4_prealloc_space *pa;
+ struct ext4_prealloc_space *pa, *tmp_pa, *prev = NULL, *next = NULL;
struct ext4_group_info *grp;
struct ext4_inode_info *ei;
+ int merged = 0;
if (ac->ac_flags & EXT4_MB_HINT_PA_ONLY) {
/* EXT4_MB_HINT_PA_ONLY makes all found space preallocated */
@@ -3508,13 +3552,65 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
pa->pa_obj_lock = &ei->i_prealloc_lock;
pa->pa_inode = ac->ac_inode;
- ext4_lock_group(sb, ac->ac_b_ex.fe_group);
- list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
- ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
+ spin_lock(&ei->i_prealloc_lock);
+ rcu_read_lock();
+ list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
+ if (tmp_pa->pa_deleted)
+ continue;
+ if (tmp_pa->pa_lstart > pa->pa_lstart) {
+ next = tmp_pa;
+ break;
+ }
+ prev = tmp_pa;
+ }
+ rcu_read_unlock();
- spin_lock(pa->pa_obj_lock);
- list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
- spin_unlock(pa->pa_obj_lock);
+ if (next) {
+ BUG_ON(pa->pa_lstart + pa->pa_len > next->pa_lstart);
+ spin_lock(&next->pa_lock);
+ merged += ext4_mb_merge_preallocations(next, pa);
+ }
+
+ if (prev) {
+ BUG_ON(prev->pa_lstart + prev->pa_len > pa->pa_lstart);
+ spin_lock_nested(&prev->pa_lock, SINGLE_DEPTH_NESTING);
+
+ if (merged) {
+ merged += ext4_mb_merge_preallocations(prev, next);
+
+ if (merged == 2) {
+ /* Prepare to discard next */
+ atomic_inc(&next->pa_count);
+ next->pa_free = 0;
+ }
+ } else {
+ merged += ext4_mb_merge_preallocations(prev, pa);
+ }
+ spin_unlock(&prev->pa_lock);
+ }
+
+ if (next)
+ spin_unlock(&next->pa_lock);
+
+ if (!merged) {
+ if (prev)
+ list_add_rcu(&pa->pa_inode_list, &prev->pa_inode_list);
+ else
+ list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
+
+ spin_unlock(&ei->i_prealloc_lock);
+ ext4_lock_group(sb, ac->ac_b_ex.fe_group);
+ list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
+ ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
+ } else {
+ spin_unlock(&ei->i_prealloc_lock);
+ ac->ac_pa = NULL;
+ kmem_cache_free(ext4_pspace_cachep, pa);
+
+ /* If prev and next are merged, discard next */
+ if (merged == 2)
+ ext4_mb_put_pa(NULL, sb, next);
+ }
return 0;
}
--
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